The most common and most likely answer to this crossword clue is the 3 plus 3 letter word ICE AGE
I've seen this crossword clue in Financial Times
I
C
E
A
G
E
More clues leading to the result ICE AGE
- One given sentence finally in jail for the 'cooler years'
- Time when all assets were frozen
- I, wise person, reported what climate change could bring
- I, wise man, said the ground would be frozen now
- Big freeze is cold and endlessly severe
- One almost impatient to catch cold in this period
- Police agent’s chill-out time?
- Period that is needed to cover church silver
- In charge, keen to shorten period of hostile conditions
- Time when all assets were frozen?
Buddy explains!

The straight part
We know that "ground would be frozen now" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ground would be frozen now = ice age.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.